Detective Inspector Greg Murton read about the findings in The Press and emailed her to say he would review the file into her brother's death.

Cartier said her confidence in police was shattered and she had to meet Murton because "I needed to know I could trust this guy".

"I couldn't go through that nightmare again - hitting my head against a brick wall, dealing with idiots," she said.

She remained in regular contact with Murton throughout the homicide investigation and recalled the morning of October 27, 2011 when he called to say that Milner had been arrested and would be charged with Nisbet's murder.

She went home and celebrated with a bottle of bubbly.

"I was totally relieved we were at that point.

"I'm so grateful for Greg. I know there was no stone unturned."

When the trial began on December 2, the jury heard it was likely Milner crushed up Phenergan tablets then mixed them in with her husband's dinner the night before his body was found.

The antihistamine and sedative killed him outright or she may have suffocated him while he was sedated, the Crown argued.

Milner then set the scene of a suicide and tried to cover her tracks by forging a suicide text and suicide notes.

The jury of seven men and five women took nearly eight hours to find her guilty of murder.

Cartier said she wanted to confront her brother's killer to put her mind at ease.

"I know why she killed him - she killed him for money.

"What in her mind made her think that it was acceptable? What made her think that she could get away with it?

"It's just hard to believe that someone like that could actually exist.

"You watch movies and she's that nutty, screwed up chick . . . that you think that someone just made up, but she's it for real.

"I think it would put my mind at ease - and it would help with my book."

Cartier hoped Milner would never be released from jail because she would always pose a risk to society.

"She's not like the nutter at the pub who has a couple of beers and flips out and starts throwing s... . You can't tell what she's up to and who knows what she's up to?" she said.

Cartier has engaged a lawyer and wants to sue the police "for expenses and the emotional stress of doing their [the police's] job".

Reflecting on the last four and half years she regretted the toll her obsession with the case had taken on her family. She felt like she had let her children down - putting the investigation before them.

"No money can pay for the time they've been robbed of," she said.

"It had to be done. No-one else was going to do it - it's just something you can't let go."

Cartier has been unemployed since moving back to New Zealand in 2012 to prepare for the trial and sold assets to fund her stay.

The saga has left her financially ruined, she said. She planned to move back to Australia.

"I thought maybe we could make New Zealand our home, but [it has] got too much to do with this whole thing."

She hoped that writing about the ordeal would allow her to move on with her life.

"If I get it all down in a book and it's there then it's out of my head, then I can let go of it. Then when people start asking [about the case] I can tell them to read my f...ing book."

But before that happens her family planned to hold another funeral for Nisbet.

"We were ripped off by the first one. It was run by a murderer. [Milner] shouldn't have been there."